The invention relates to a non-dusting homogeneous pigment preparation notable in that it comprises at least 40% by weight of one or more effect pigments, 0.5-50% by weight of water and/or an organic solvent or solvent mixture, and 0.5-59.5% by weight of a styrene-modified maleate resin having an acid number of  greater than 90 mg KOH/g based on the pigment. Pigment preparations of this kind are particularly suitable for producing dry preparations, such as granules or chips, for example. The invention further relates to the production of the pigment preparation and the granules and to the use thereof for pigmenting printing inks.
In industrial processes, pigments are often not employed in the form of dry powders, since such powders produce dust, which results in heightened requirements in terms of workplace safety. In many cases, furthermore, when introducing powders into plastics, printing inks, industrial coatings, basecoat systems, etc., agglomeration of the pigment powder is observed. Homogeneous distribution of the pigment in the respective matrix is frequently difficult if not impossible to achieve.
Instead of the pigment powder, non-dusting pigment formulations or dry preparations are used. These are
free-flowing powders, pearl lustre pigments being coated with polymers, as are described, for example, in DE-C-2603211,
pigmented free-flowing powders having a low moisture content, as are known, for example, from DE-A-4139993,
pigmented powders having a relatively high moisture content, which owing to their flowable consistency are frequently referred to as pastes,
pigment formulations in granule form, in which organic pigments are coated with a resin mixture, as disclosed, for example, in EP 0 897 956 A2, or
dry preparations, such as pellets, granules as precursors for printing inks, as are known, for example, from EP 0 803 552.
Non-dusting homogeneous pigment preparations and dry preparations prepared from them are an industrial alternative to the dry or moistened powders provided that they meet the following general conditions:
flowable consistency
minimal dilatancy
maximum pigment content
The components of the preparation/paste, or of the dry preparations, should be chosen such that the formulation is harmonized very effectively with the other components of the respective coating system and is readily homogeneously distributed following its introduction.
In addition to good compatibility with the other constituents of the coating system, pigment preparations, and the dry preparations produced from them, are required to result in high stability in the coating systems, i.e., they must not tend towards phase separation, or, where this cannot be entirely prevented owing to the low viscosity, the coating systems must be able to be returned easily to a homogeneous state, i.e., the settled sediment must be easy to reagitate. This requirement is particularly important in the case of platelet-shaped pigments, since owing to their structure such pigments have a tendency to undergo xe2x80x9ccakingxe2x80x9d on phase separation and are difficult to reagitate. Pigments based on platelet-shaped substrates give rise to handling problems insofar as, owing to the size and density of the pigments, they readily settle and may then cake together to form a very firm sediment cake. This cake is generally difficult to reagitate. This is particularly so in connection with the storage of varnishes, paints and printing inks, as well as In connection with their processing.
For this reason, numerous methods, inter alia, have been developed in order to solve the problem of the incorporation and handling of platelet-shaped pigments in coating compositions. Reagitation can be facilitated by adding to the coating compositions additives which alternatively bring about controlled flocculation (house of cards effect), pseudoplastic and/or thixotropic behaviour, or steric and/or electrostatic repulsion of the pigments. However, these additives may have an adverse effect on the quality of the coating. In particular, the brilliance in the case of effect pigments, and the uniformity of the coating, may be impaired.
In addition, homogeneous, stable distribution of the redispersants in the pearl lustre pigment powder is difficult to achieve, and/or the redispersant loses some of its activity in the course of mixing.
The effect pigment formulations developed to date for use in coating systems, with a pigment content  greater than 30% by weight, frequently do not go far enough towards meeting the requirements described above, especially since they have a tendency towards agglomeration and shear thickening.
The object of the present invention was therefore to provide pigment preparations, especially those in the form of formulations or pastes and dry preparations, which simultaneously can be used very effectively in aqueous, solventborne and solvent-free printing ink and coating systems, possess high stability, are easy to redisperse, and at the same time feature a high level of compatibility with the other components of the coating system. Furthermore, the pigment preparation of the invention ought also to be highly suitable for producing dry preparations in the form, for example, of pellets, granules, etc.
It has surprisingly been found that this object can be achieved by the provision of the pigment preparation of the invention. Styrene-modified maleate resins exhibit, in combination with effect pigments, such as pearl lustre pigments, for example, universal compatibility in aqueous, solventborne and solvent-free printing ink and coating systems. In addition, the formation of the interference effect in the case of pearl lustre pigments is promoted.
The invention therefore provides a non-dusting homogeneous pigment preparation which comprises
xe2x89xa740% by weight of one or more effect pigments,
0.5-59.5% by weight of a styrene-modified maleate resin having an acid number  greater than 90 mg KOH/g,
0.5-50% by weight of water and/or an organic solvent or solvent mixture,
0-10% by weight of neutralizing agent(s), and
0-10% by weight of modifying agent.
Depending on its moisture content, the preparation of the invention is a flowable paste or a moistened, free-flowing powder. Both are highly suitable for producing dry preparations, e.g. granules, pellets, briquettes. The use of styrene-modified maleate resins specifically in the production of non-dusting pigment granules enables better compounding to be achieved than with the polymer resins known from the prior art, as disclosed, for example, in EP 0 803 558 A1. The dry preparations produced from the pigment formulation of the invention are likewise provided by the invention.
Moreover, the products of the invention are non-dusting, readily free-flowing, can be incorporated rapidly into commercially available binder systems, and are compatible therein. In particular, the products are compatible with aqueous, solventborne and also solvent-free printing ink and coating systems. The paints and varnishes produced from the dry preparation, e.g. granules or chips, are suitable for gravure, flexographic and screenprinting, offset overprint varnishes, overprint varnishes (OPVs), and also the various coating systems from the industrial coatings and automotive sector. They are also suitable for colouring plastics.
The pigment preparation of the invention contains preferably 40-98% by weight of effect pigments, especially 45-95% by weight, based on the preparation. Very particular preference is given to pigment preparations having an effect pigment content of more than 50% by weight. The percentages by weight are based in each case on the moist, i.e. undried, pigment preparation.
Effect pigments used are pigments based on platelet-shaped, transparent or semi-transparent substrates comprising, for example, sheet silicates, such as mica, synthetic mica, talc, sericite, kaolin or other silicatic materials, platelet-shaped iron oxide, SiO2 flakes, TiO2 flakes, graphite flakes, Fe2O3 flakes, Al2O3 flakes, glass flakes, holographic pigments, which are coated with rare earth metal sulphides such as, e.g., Ce2S3, coloured or colourless metal oxides, e.g. TiO2, titanium suboxides, titanium oxyritrides, Fe2O3, Fe3O4, SnO2, Cr2O3, ZnO, CuO, NiO, and other metal oxides, alone or in a mixture in one uniform layer or in successive layers (multilayer pigments). The multilayer pigments are known, For example, from the German unexamined laid-open specifications DE 197 46 067, DE 197 07 805, DE 197 07 806 and DE 196 38 708. Pearl lustre pigments based on mica flakes are known, for example, from the German patents and patent applications 14 67 468, 19 59 998, 20 09 566, 22 14 454, 22 15 191, 22 44 298, 23 13 331, 25 22 572, 31 37 808, 31 37 809, 31 51 343, 31 51 354, 31 51 355, 32 11 602, 32 35 017 and P 38 42 330 and are obtainable commercially, e.g. under the brand names Minatec(copyright) and Iriodin(copyright) from Merck KGaA, Darmstadt, FRG.
Particularly preferred pigment preparations comprise TiO2/mica, Fe2O3/mica and/or TiO2/FE2O3 mica pigments. The SiO2 flakes can be coated, for example, as described in WO 93/08237 (wet chemical coating) or DE-A 196 14 637 (CVD process). Al2O3 flakes are known, for example, from EP 0 763 573. Platelet-shaped substrates coated with one or more rare earth metal sulphides are disclosed, for example, in DE 198 10 317.
Also suitable are metal effect pigments, especially aluminium flakes modified for aqueous systems, as sold by Eckart under the brand name Rotovario Aqua(copyright) or Stapa Hydroxal for aqueous applications, and also Variocrom(copyright) and Paliocrom(copyright) pigments from BASF, including in particular those from the laid-open specifications EP 0 681 009, EP 0 632 110, EP 0 634 458, and also LCP (liquid crystal polymer) pigments. Likewise suitable, furthermore, are all platelet-shaped pigments known to the person skilled in the art which have metal layers. Pigments of this kind are sold by the companies Flex, BASF, Eckart and Schlenk.
The pigment preparations of the invention may comprise one or more effect pigments. In many cases it is possible by using at least two different effect pigments to obtain special colour effects and lustre effects. Preferred pigment preparations comprise one or more effect pigments based on mica and/or SiO2 flakes. Blends with up to 10% by weight of organic and inorganic pigments, based on the pigment preparation, are also possible.
In particular, the addition of one or more dyes and/or organic pigments, such as Mikrolith (Ciba) or Hydrocolor/Solcolor preparations from MK Chemical, for example, in dispersed form leads to special colour effects. It is also possible to add substances and particles (tracers) which enable the product to be identified (product protection).
As a mandatory component, the pigment preparation of the invention comprises a styrene-modified maleate resin having an acid number  greater than 90 mg KOH/g in amounts of from 0.5 to 59.5% by weight, preferably from 5 to 40% by weight, in particular from 10 to 30% by weight. Particular preference is given to styrene-modified polyacrylate resins having an acid number of  greater than 100, in particular of  greater than 150.
The styrene-modified maleate resins used have an average molecular weight of from 500 to 200,000, preferably from 1000 to 100,000, in particular from 1000 to 50,000. Styrene-modified maleate resins having a molecular weight of from 2500 to 3500 are very particularly preferred. In the case of otherwise identical properties, the polymers having a low molecular weight are preferred, since they generally have a smaller thickening effect in the coating systems.
The styrene-modified maleate resins are prepared by free-radical addition polymerization, especially copolymerization or terpolymerization, in the course of which it is possible to incorporate saturated and unsaturated alcohols and also other functionalizations in broad mass proportions. In particular, polyethylene and polypropylene units, or mixtures of alkylene oxides, can also be incorporated into the polymer framework, as can alkylene oxide esters, alkylene oxide amines, alkylene oxide ethers, and free carboxyl groups. This incorporation is in particular of great advantage for the compatibility of the products of the invention in aqueous systems. The styrene-modified maleate resins preferably have a styrene to maleic anhydride ratio of from 1:1 to 4:1. The styrene-modified maleate resins thus prepared are notable for their light stability (yellowing resistance), their resistance to oxygen (storage stability), their resistance to self-ignition, and by their low static charging.
xcex1-Methylstyrene-modified maleate resins are particularly suitable. Preference is given, in accordance with the invention, to the use of resins having a glass transition temperature which is above room temperature. This rules out blocking and deficient free-flow capabilities of the dry preparation. For instance, the maleate resins used have a glass transition temperature of preferably 35-170xc2x0 C., in particular 40-80xc2x0 C. The softening point of the resins used is preferably 45-180xc2x0 C., in particular 50-90xc2x0 C.
The styrene-modified resins are also obtainable commercially, for example, under the brand name SMA(copyright) from Elf-Atochem.
It is further advantageous if the pigment preparation of the invention contains from 0 to 10% by weight, preferably from 0.05 to 5% by weight, in particular from 0.01 to 3% by weight, of a modifier. The modifier used is in particular a polyalkylene oxide or derivative thereof, in order to increase the strength, compatibility and dissolution rate of the dry preparations. Further suitable modifiers are reagitability-enhancing resins such as rosins, urethane resins, nitrocellulose and all known cellulose derivatives, polyesters, PVC, sulpho polyesters, polyethylene glycol esters and ethers, emulsifiers and surfactants in amounts of from 0.1 to 10% by weight, preferably from 0.05 to 5% by weight, in particular from 0.01 to 3% by weight, based on the preparation.
In particular, it is also possible to add to the pigment preparation according to the invention substances which accelerate or assist the breakdown and dissolution of the pigment granules, examples being bulky spherical particles, such as hollow beads, hemispherical beads, swellable substances with a strong swelling power, substances which undergo controlled breakdown and in doing so evolve gases, and/or substances having very high solubility.
As a further component, the pigment preparation of the invention or dry preparations produced from it preferably include one or more neutralizing agents. Particularly suitable agents are the bases common in the coatings sector, such as urea, urea derivatives, ammonia, amino alcohols, alkali metal hydroxides, such as KOH or NaOH, and amines, for example; in the case of preparations for aqueous applications, the bases are preferably nonvolatile organic amines of low molecular mass or amines of this kind whose volatility at 100xc2x0 C. is low.
The acid number of the modified maleate resin in conjunction with the neutralizing agent gives the resins water solubility. Water solubility in accordance with the present invention is on the one hand important in connection with the preparation process, in order to permit an aqueous route, while on the other hand the water solubility is a prerequisite for use in aqueous and waterborne printing ink systems (compatibility).
In general, the pigment preparation of the invention contains from 0 to 10% by weighs of a neutralizing agent, preferably from 1 to 7% by weight, in particular from 1 to 5% by weight, based on the pigment preparation.
If necessary, the addition of a redispersing aid in the form of bulky particles, such as fibres or spherical particles, for example, prevents the effect pigments treated in accordance with the process of the invention from lying on top of one another to a notable extent as a result of steric repulsion and so exerting strong adhesion. The result of this is that
1. the preparations of the invention are more stable, and
2. owing to the introduction of the redispersing aid into the paint or varnish system by way of the pigment preparation, the effect pigments settle more slowly, in some cases very much more slowly, in paint and varnish systems;
in all cases, however, the sediment is less hard, and no problems occur when the sediment is reagitated.
The redispersant is preferably used in amounts of from 0 to 5% by weight, in particular from 0.05 to 3% by weight, based on the pigment preparation. All organic and inorganic fibres known to the person skilled in the art and having a fibre length of 0.1-20 xcexcm can be used. Particularly suitable particles are all synthetic fibres, made for example from polyethylene, polyacrylates, polypropylene, polyamides, cellulose fibres, inorganic fibres, preferably silicon compounds, glass fibres, and also, in particular, the condensation products of modified isocyanates and mono- and diamines. These condensation products, which are diurea derivatives and aminoureas having urethane groups, are known as thixotropic agents and, together with a binder, are added to paints and varnishes in order to improve the running properties and the brushability.
Redispersing aids which can be used are all those diurea derivatives and urethane compounds known to the person skilled in the art, as are described, for example, in EP 0 198 519, DE 18 05 693.4, and in Organic Coatings: Science and Technology, A. Heenriga, P. J. G. von Hemsbergen, pp. 201-222, New York 1983.
Suitable spherical materials are, in particular, hollow glass, wax or polymer beads made from vinyl resins, nylon, silicone, epoxy resins, olefin resins and polystyrenes, and from inorganic materials, such as TiO2, SiO2 or ZrO2, for example. Preference is given to the use of hollow beads, and also solid beads, having a particle size of from 0.05 to 150 xcexcm. With particular preference, hollow glass, wax or polymer beads are used in the pigment preparation of the invention.
Spherical particles based on SiO2 in a particle range of 3-10 xcexcm are known, for example, as materials for high-performance liquid chromatography and are sold, for example, as LiChrospher(copyright) by Merck KGaA, Darmstadt, FRG. Such materials are preferably used in monodisperse form; that is, with a substantially uniform particle size. Monodisperse spherical particles of this type based on SiO2, TiO2 and ZrO2 are known. Monodisperse SiO2, for example, can be prepared in accordance with DE 36 16 133. Hollow glass beads are sold, for example, under the trade name Q-CEL by PQ Corporation, USA, or Scotchlite by 3M, Frankfurt, FRG.
In addition, the pigment preparation of the invention may comprise surface-active substances, such as alkylsilanes, for example, which may also contain a further functional group, or unsaturated or saturated fatty acids or fluorosurfactants. Particular preference is given to the use of silane compounds of the formula (CnH2n+1)Si(OCmH2m+1)3, where n is 1-30 and m is 1-10, as surface-active substances. Examples of suitable silane compounds are n-hexyldecyltriethoxysilane and n-octyldecyltriethoxysilane (Si 116 and Si 118, respectively, from Degussa AG, Frankfurt, FRG), and also the corresponding fluoroalkylsilanes.
In addition to the silane, the pigment preparation gigs preferably further comprises a surfactant or a fatty acid. The surface-active reagent may also comprise a mixture of silane, fatty acids and/or surfactants. The pigment preparations can contain from 0.1 to 5% by weight, preferably from 0.2 to 3% by weight and, in particular, from 0.5 to 2% by weight of surface-active substances, based on the preparation.
Further surface-active substances which may be used are the saturated and unsaturated fatty acids, such as capronic acid, caprylic acid, capric acid, lauric acid, myristic acid, palmitic acid, stearic acid, oleic acid, linoleic acid, and also fatty acid mixtures, for example.
The pigment preparation of the invention contains from 0.5 to 50% by weight of water and/or an organic solvent or solvent mixture, preferably from 1 to 45% by weight, in particular from 1 to 40% by weight, based on the preparation.
The solvent component in the pigment preparation of the invention must be properly matched to the resin having an acid number  greater than 90 mg KOH/g. For the preparation, water and all organic solvents can be used depending on the polyacrylate resin employed. Examples of suitable solvents are aromatic solvents such as toluenes, benzines, xylenes, hydrocarbons and also esters, cyclohexane, furans, dioxanes, chlorinated hydrocarbons, long-chain amines, vegetable oils, monohydric aliphatic alcohols, such as those having 2 to 4 carbon atoms, e.g. ethanol, butanol or isopropanol, or ketones, e.g. acetone or methyl ethyl ketone, or glycol ethers, such as propylene glycol monomethyl ether, propylene glycol monoethyl ether, or diols, such as ethylene glycol and propylene glycol or polyether diols, aliphatic triols and tetraols having 2 to 6 carbon atoms, such as trimethylolethane, trimethylolpropane, glycerol, 1,2,4-butanetriol, 1,2,6-hexanetriol and pentaerythritol, and all other solvents from other classes of compound, or mixtures of the abovementioned solvents. It is preferred to use those solvents that are listed in Karsten, Lackroh-stofftabellen, 9th edition 1992.
The pigment preparation of the invention is produced in a simple manner by adding the modified maleate resin, with or without water and/or an organic solvent or solvent mixture, a modifier and, if desired, further additives, simultaneously or in succession to the effect pigment or effect pigment mixture and subjecting the resulting mixture to gentle homogenization in a mixing apparatus.
Preferably, the pigment is introduced as initial charge and first pasted up, with stirring, with the water and/or the organic solvent or solvent mixture comprising the maleate resin, and possibly even at this stage the modifier; subsequently, if desired, a further solution consisting of water and/or solvent and additives is added.
During or after its productions further customary additives may be added to the pigment preparation of the invention, examples being defoamers, wetting agents, anti-settling agents, levelling agents, siccatives and thixotropic agents. These are auxiliaries which are customary in the coatings industry and which may be present in the pigment preparation of the invention in an amount of from 0 to 10% by weight. Mention is made here in particular of succinate derivatives, examples being those as sold by Henkel under the brand name Hydropalat 875.
The resultant moist pigment preparation of the invention is a homogeneous powder, or readily flowable pastes, having a relatively high effect pigment content. Because of the particularly high level of compatibility of the styrene-modified maleate resin, the pigment preparation of the invention is likewise thoroughly compatible with commercially customary aqueous, solventborne and solvent-free printing ink systems. Further features which distinguish the preparation are its freedom from dust, ready dispersibility and ready redispersibility, and it is therefore markedly superior to conventional pigment preparations.
In order to produce dry preparations, the pigment preparation of the invention is extruded or, by other methods known to the person skilled in the art, compressed into a compact particulate form by means, for example, of tabletting, briquetting, pelletizing, granulating, spray-granulating, fluidized-bed granulating, or extrusion, and may then be dried. The drying procedure generally takes place at temperatures from 20xc2x0 C. to 150xc2x0 C., preferably at from 60 to 120xc2x0 C., and can if desired be carried out under reduced pressure. The dry preparations, such as chips, pellets, briquettes or granules, for example, have a residual moisture content of not more than 5% by weight, preferably  less than 3% by weight. The granules have pigment contents of  greater than 70% by weight, preferably of  greater than 80% by weight, based on the granules. Finally, the dry preparation is, if desired, classified. The dried granules obtained in this way have positive properties which are further increased relative to the water and/or solvent-containing preparations: the absence of liquid components increases the compatibility. Dry granules in particular also, surprisingly, showed no disadvantages in terms of wetting. On the contrary, when added to an aqueous binder or to a binder based on polar solvents (ethanol, ethyl acetate, MEK, etc.) the granule breaks down rapidly and there is immediate and complete wetting. Further advantages of a dry formulation are the improved storage stability, the easier transportation, and the improved product safety for the customer. Granules, in bead form for example, are very readily free-flowing, easy to meter, and combine all of these properties with the total absence of dust. The volume of these granules is reduced to about ⅓ of the volume of pearl lustre pigment powders. The particle sizes of the dry preparations are in the range of 0.1 to 150 mm, preferably 0.1-20 mm, in particular 0.1-2 mm.
In addition to their ready compatibility with the coating systems and the synergy effects with the other components in the pigment preparation or in the dry preparation, the high acid number of the styrene-modified maleate resin enables the resins to be converted, together with neutralizing agents, into a water-soluble form. The production of the dry preparations, such as granules, chips, pellets or briquettes, for example, can therefore be completed by an aqueous route, which offers considerably greater production safety as compared with the use of solvents.
The integration of a redispersing aid ensures that even in the finished varnish and paint systems the pigment preparations of the invention are easy to stir and require no further improvement by the end formulator.
The improved deagglomeration of the dry preparations when incorporated into a binder, such as into a printing ink, is evident even with small amounts of spherical particles in the pigment preparation. For instance, even when using granules having a spherical particle content of 0.5% by weight based on the dry preparation, the dissolution rate is markedly increased and the stability of the printing ink is attained more rapidly (viscosity/hue).
The dry preparations are non-dusting, readily free-flowing, can be incorporated rapidly into commercially available binder systems, and are compatible therein. In particular, the products are compatible not only with aqueous and solventborne but also with solvent-free printing inks and coating systems.
As a paste or as a dry preparation, the preparation of the invention can be used for diverse applications. It is preferably used in coating systems from the sectors of printing, especially overprint varnishing, offset overprint varnishing, and gravure, flexographic and screenprinting. With particular preference, the preparation or the dry preparation produced from it is applied as a precursor for coating compositions on any desired substrate materials, examples being metals such as iron, steel, aluminium, copper, bronze; plastic; brass and also metal foils, and also glass, ceramic and concrete, and also on wood, e.g. furniture, clay, textile, paper, packaging materials, e.g. plastic containers, films or boards, or on other materials for decorative and/or protective purposes.
The invention therefore also provides for the use of the pigment preparation in formulations such as paints, varnishes, printing inks and plastics, and also automotive finishes, powder coating materials and coating compositions in general.
The examples which follow are intended to illustrate the invention without, however, restricting it.